The invention relates to apparatus for processing relating to a stream of bits.
Bits in a stream that are transmitted from one processor to another typically need to be filtered (i.e., analyzed to determine what they mean) and processed in some manner based upon the result of the filtering. E.g., in a computer network (e.g., as described in Tanenbaum, A. S., Computer Networks, (Prentice-Hall, Inc. 1981), pp. 10-28 ("Tanenbaum")), the filtering of an incoming bit stream occurs in the lower layers of the network processor at a node; if the incoming bits are identified as being of interest to the node (e.g., having a destination address associated with the node in an address field of a frame of bits), the bits are stored and later used by upper layers.
In the local area network controller for Ethernet ("LANCE"), which is described in MOS Microprocessors and Peripherals 1985 Data Book, (Advanced Micro Devices, Inc., Sunnyvale, Calif. 1985) pp. 2-50 to 2-86 ("LANCE Specification", which is hereby incorporated by reference), the 48-bit Ethernet address is analyzed in a bit-by-bit compare, and frames that do not have addresses that match are discarded. When an address matches all the way through to the last bit in the address field, the frame is placed in data buffers for access by the upper layers. The upper layers do not know which address matched, only that one did. Thus the software associated with the upper layers must repeat the entire compare process.